Magnetic and magneto-optical media are extensively employed in the computer industry and can be locally magnetized by a write transducer or write head to record and store information. The write transducer creates a concentrated magnetic field which is directionally alternated based upon specific bits of the information being stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the recording medium, grains of the recording medium at that location are magnetized. The grains retain their magnetization after the magnetic field produced by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The magnetization of the recording medium can subsequently produce an electrical response to a read sensor, allowing the stored information to be read.
Magnetic recording media with higher storage capacity, less noise when reading or writing and lower production cost is increasingly in demand. Therefore, efforts have been made to reduce the size (e.g., nanometer range) of recording media required to magnetically record bits of information. Also, the integrity of the information must be maintained as size is decreased. The space necessary to record information in magnetic recording media depends upon the spacing of transitions between oppositely magnetized areas. Generally, these transitions are nanometers in size. It is, therefore, desirable to produce magnetic recording media that will support the smallest transition size possible. However, the output transitions from smaller recording media must avoid excessive noise (generally expressed in signal-to-noise ratio (SMNR)) to reliably maintain the integrity of the stored information.
In general, achieving a magnetic recording media having acceptable characteristics involves microstructural and crystallographic control of the media materials during a deposition process. Such control is typically attempted by manipulating the deposition process and proper use of underlayers and seedlayers (e.g., templating the magnetic layer). In spite of these improved techniques for higher quality media, such as less noise and higher storage capacity, traditional perpendicular media remains the deposited material.
Tilted perpendicular media has been proposed as a means to write higher anisotropy magnetic recording media than otherwise possible using conventional perpendicular recording schemes, since more grains are distributed along a similar magnetic path. Therefore, smaller grain size and higher areal density of tilted perpendicular media has an extended thermal stability compared to conventional perpendicular media. The basic advantage of the tilted geometry is suggested by the dependence of the switching field on the applied field angle, graphically shown for an ideal Stoner-Wohlfarth particle in FIG. 1. The graph contains several regions, such as region 2 for conventional perpendicular overwrite media, region 4 for conventional perpendicular writing media and region 6 for tilted perpendicular writing and overwrite media. Ideally, a minimum switching field of ½Hk=K/Ms is realized for an applied field direction of 45° to the particle magnetic easy axis, where K is the uniaxial anisotropy constant and Ms is the saturation magnetization. This minimum value is one-half the maximum switching field of Hk=2K/Ms, realized for an applied field direction of 0°, i.e., head-on to the easy axis. Conventional perpendicular recording structures using a soft magnetic underlayer and perpendicular easy axis for the recording layer typically operate close to the head-on geometry, where switching is in fact least efficient.
Region 2 depicts conventional perpendicular overwrite media with head-on geometry and a write field of 5°±6° with respect to media Hk. Region 4 depicts conventional perpendicular writing media with a slightly lower switching field than perpendicular overwrite media. Conventional perpendicular writing media has a slight geometric grade and a write field of 12°±6° with respect to media Hk. However, region 6 depicts titled perpendicular writing and overwriting media with only about 50% of the switching field than that required in conventional perpendicular overwrite media. The ideal write field is about 45°±8° with respect to media Hk. Therefore, the minimum switching field is achieved as the field angle increases to 45°. Hence, the use of tilted symmetry material will inherently minimize the switching field. The art is deficient while providing adequate processes and apparatuses to deposit tilted perpendicular media.
Therefore, there is a need for an apparatus and method for depositing tilted symmetry material on a magnetic recording medium. Furthermore, there is a need to control the angle the material is deposited to the substrate.